[🐛 Bug]: [py] Unable to set window position in Firefox

[cgoldberg]

Description

When you call driver.set_window_position(x, y) using Firefox, the window position is not set. I am pretty sure this is a geckodriver issue, and I already reported it:

mozilla/geckodriver#2224

I am just reporting it here to track the issue on the Selenium side and will close this once fixed.

The following test is failing in Selenium's Python/Firefox CI job because of this:

FAILED py/test/selenium/webdriver/common/api_example_tests.py::test_move_window_position[firefox] - assert 0 == 50

Reproducible Code

from selenium import webdriver

driver = webdriver.Firefox()
driver.set_window_position(50, 50)

Debugging Logs

Selenium Manager binary found at: /home/cgoldberg617/code/selenium/py/selenium/webdriver/common/linux/selenium-manager
Executing process: /home/cgoldberg617/code/selenium/py/selenium/webdriver/common/linux/selenium-manager --browser firefox --debug --language-binding python --output json
geckodriver not found in PATH
firefox not found in PATH
firefox not found in the system
Required browser: firefox 137.0
firefox 137.0 already exists
firefox 137.0 is available at /home/cgoldberg617/.cache/selenium/firefox/linux64/137.0/firefox
Required driver: geckodriver 0.36.0
geckodriver 0.36.0 already in the cache
Driver path: /home/cgoldberg617/.cache/selenium/geckodriver/linux64/0.36.0/geckodriver
Browser path: /home/cgoldberg617/.cache/selenium/firefox/linux64/137.0/firefox
Started executable: `/home/cgoldberg617/.cache/selenium/geckodriver/linux64/0.36.0/geckodriver` in a child process with pid: 26445 using 0 to output -3
POST http://localhost:53805/session {'capabilities': {'firstMatch': [{}], 'alwaysMatch': {'browserName': 'firefox', 'acceptInsecureCerts': True, 'moz:debuggerAddress': True, 'pageLoadStrategy': <PageLoadStrategy.normal: 'normal'>, 'browserVersion': None, 'moz:firefoxOptions': {'binary': '/home/cgoldberg617/.cache/selenium/firefox/linux64/137.0/firefox', 'prefs': {'remote.active-protocols': 3}}}}}
Remote response: status=200 | data={"value":{"sessionId":"1d307608-760e-4f31-970a-d8bc7290d74f","capabilities":{"acceptInsecureCerts":true,"browserName":"firefox","browserVersion":"137.0","moz:accessibilityChecks":false,"moz:buildID":"20250327043313","moz:debuggerAddress":"127.0.0.1:49303","moz:geckodriverVersion":"0.36.0","moz:headless":false,"moz:platformVersion":"6.6.67-06628-g571b599e617d","moz:processID":26448,"moz:profile":"/tmp/rust_mozprofile39S6FX","moz:shutdownTimeout":60000,"moz:webdriverClick":true,"moz:windowless":false,"pageLoadStrategy":"normal","platformName":"linux","proxy":{},"setWindowRect":true,"strictFileInteractability":false,"timeouts":{"implicit":0,"pageLoad":300000,"script":30000},"unhandledPromptBehavior":"dismiss and notify","userAgent":"Mozilla/5.0 (X11; Linux x86_64; rv:137.0) Gecko/20100101 Firefox/137.0"}}} | headers=HTTPHeaderDict({'content-type': 'application/json; charset=utf-8', 'cache-control': 'no-cache', 'content-length': '814', 'date': 'Mon, 07 Apr 2025 03:46:45 GMT'})
Finished Request
POST http://localhost:53805/session/1d307608-760e-4f31-970a-d8bc7290d74f/window/rect {'x': 50, 'y': 50, 'width': None, 'height': None}
Remote response: status=200 | data={"value":{"x":0,"y":0,"width":488,"height":240}} | headers=HTTPHeaderDict({'content-type': 'application/json; charset=utf-8', 'cache-control': 'no-cache', 'content-length': '48', 'date': 'Mon, 07 Apr 2025 03:46:49 GMT'})
Finished Request

[selenium-ci]

@cgoldberg, thank you for creating this issue. We will troubleshoot it as soon as we can.

Selenium Triage Team: remember to follow the Triage Guide

[cgoldberg]

This is happening because it is not possible to programatically set the window position when running under the Wayland display server (Linux).

There is now an issue open for Firefox to display a better error message in this circumstance:

https://bugzilla.mozilla.org/show_bug.cgi?id=1959040

[cgoldberg]

I am re-opening this because setting window position is still broken in Firefox on Linux, whether you are running Wayland or not:

mozilla/geckodriver#2224

The following test files in the internal test suite have failures because of this:

py/test/selenium/webdriver/common/window_tests.py
py/test/selenium/webdriver/common/api_example_tests.py

(you can see failures in recent CI runs)